1. Field of the Invention
The present invention relates generally to the field of electro-mechanical actuators, and, more particularly, to an improved electro-mechanical actuator capable of being latched in its extreme positions, and also capable of proportional operation within an operating range.
2. Description of the Prior Art
Heretofore, others have developed various forms of electro-mechanical actuators and solenoids. Such earlier efforts are shown in one or more of the following U.S. Pat. Nos.: 2,735,045 (Savoie); 3,368,788 (Padula); 3,481,578 (Baldi); 3,502,105 (Ernyei et al.); 3,751,086 (Geringer); 3,814,376 (Reinicke); 3,859,547 (Massie); 3,886,507 (Johnston et al.); 4,203,571 (Ruchser); and 4,216,938 (Inada et al.). Of these, Reinicke interposed a permanent magnet between two energizable coils. A single magnet provided two magnetic loops, each encircling a coil. With respect to the magnetic circuits disclosed and claimed herein, British Pat. No. 1,008,735 (Hamilton et al.) and U.S. Pat. No. 4,127,835 (Knutson) may also be pertinent.
Rare earth magnets, such as those formed of samarium cobalt, have been developed in recent years. These magnets afford the capability of an intense field strength from a physically-smaller magnet. However, unlike most iron alloys, these new materials generally have a very high reluctance, or impermeability to passage of magnetic flux therethrough. Indeed, their permeability to flux passage is on the same order of magnitude as that of air. See, e.g., Yamada, "The Situation of Rare Earth-Cobalt Magnets in Japan", informiert, Th. Goldschmidt A. G., No. 48 (February 1979) [at 43, 44-46]. Hence, when positioned in a magnetic circuit, such rare earth magnets may, for practical purposes, be regarded as the equivalent of an air gap to passage of flux therethough. Other specific types of such rare earth magnets, and their properties and characteristics, are also listed in informiert, supra.
As they have become available, others have heretofore employed such rare earth magnets in a variety of different devices. Examples of these earlier implementation schemes are shown in British Pat. No. 1,591,471 (Hart) and U.S. Pat. No. 4,144,514 (Rinde et al.), both of which disclose types of electro-mechanical actuators employing samarium cobalt magnets.